Later in the day, the 40-foot-tall containment dome will be lowered by a huge crane onto the spouting wellhead.

Although a containment device has never been used so far below the surface, the company that made it -- Wild Well Controls -- believes that this one can capture and then pipe up to waiting tankers a substantial amount of the oil that would otherwise be released to the sea.

Given the large and steady stream of oil coming out from the rupture, the well-being of thousands of Gulf Coast residents and countless creatures that live in the hyper-fertile region depend on the box's success. Louisiana officials announced Thursday that they had discovered two more dead birds, covered in oil, near the Grand Gosier Islands.

Coast Guard Rear Adm. Mary Landry tried to moderate expectations that the containment device would be a silver bullet.

"I know we are all hoping that this containment system will work, but I want to remind everybody that this containment system is a first of its kind deployed in 5,000 feet of water," Landry said, according to the Associated Press.

The waters at the spill site were calm Thursday morning, AP reported. A spokesman for BP, which is working to contain the oil spill, told the news service that the drop is expected after noon Thursday.

The device is the latest of a broad range of techniques being used to staunch the oil leak, created by the explosion of the Transocean Deepwater Horizon Rig on April 20, killing 11 workers.

The launch Wednesday night of the gleaming box from Port Fourchon, an industrial hub at the very southern tip of Louisiana, captured the uneasy balance of forces at work here, where the marshlands hit the sea.

The barge inched away from the Wild West yard along a canal flanked by cranes, discarded oil rigs, tank farms and endless barbed wire -- a gas industry outpost of heavy equipment and hard-hat men. Helicopters come in and out regularly to the port, and oil rigs are visible on the horizon. The dome, which was used in shallower waters during Hurricane Katrina, was modified at the Wild Wells yard. Two more are being prepared.

The barge then traveled the Bayou Lafourche to the deeper waters, passing some of the most fertile marshes in the nation -- where fish and crustaceans of all kinds flourish in the rich outflow of the Mississippi River. One side of the bayou is an industrial park; the other side part of a national park.

The road down to Port Fourchon runs alongside another bayou, now filled with hundreds of fishing boats. They supply a significant percentage of the nation's seafood, but are now unable to go out to work. Even the harshness of Port Fourchon cannot eliminate the fertility of the land: Drainage ditches filled with trash and garbage still are alive with crabs and schools of darting fish.

While fishermen have been vocal in their dismay about the spill, the army of workers at Port Fourchon were officially mum as the dome moved out. Wild Wells referred all questions to the Unified Command Deepwater Joint Information Center many miles away in Robert, La., and workers from companies nearby said they were told not to speak with reporters.

One man, however, offered this reminder: "You know," he said, after speaking on the condition of anonymity, "we have as much riding on this as the fishermen and beachfront folks. If this can be controlled, we go back to business like before. If it creates a big mess, we're in big trouble for quite a while."